[Info-vax] Intel junk...Kernel-memory-leaking Intel processor design flaw forces Linux, Windows redesign

[Neil Rieck]

I don't want to sound like an old fart, but the first computer I ever worked on (Interdata Model 70) did not have an Operating System. My first exposure to a true OS was RT-11 and RSX-11M in the late 1970s during classes at DEC "ed-services" in Kanata Ontario and Bedford Massachusetts.

Around that time, many of us hobbyists were playing with 6502 and 6800 micros at home. I recall someone asking the DEC instructor why micros appeared to be so much faster than minis. His paraphrased response went something like this:

DEC hardware and software was built assuming that every user (in a multi-user system) was doing something dangerous like learning MACRO programming which could crash the whole system. This meant that sufficient memory management hardware was built into the system (along with supporting software) so that a crash would only occur in user-space. Also, memory management was used to isolate the memory used by various processes for security reasons.

I moved from the 6502 to the MC68000 which also didn't have built-in hardware although it was available with external chips (MC68851). Later chips starting with the MC68020 claimed to have built-in memory management which rivaled features we saw in minis but those were all CISC machines.

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One of the latest exploits is called Spectre and (apparently) deals with speculative execution of code in RISC and other non-CISC systems. In effect, CPU caches are being used as a back-channel to snoop data left behind by other processes. So obviously the memory protection paradigm built into CISC systems was not fully extend to all subsystems of non-CISC platforms.
 
Perhaps some technical guru can comment as to how memory protection was implemented in caches on Alpha and Itanium.
 
Neil Rieck
Waterloo, Ontario, Canada.
http://neilrieck.net